The present invention relates to a self-lubricating composite material, and in particular to a self-lubricating composite material prepared from polymers.
Bearing members made from self-lubricating composite material prepared from polymers have become popular in the friction and lubrication field, because they are self-lubricating, rust-resistant, light in weight, easy-to-produce, low in cost and very compatible. A large percentage of conventional metal bearing members have been gradually replaced by bearing members made from self-lubricating material using polymers as matrix.
Current self-lubricating materials prepared from polymers are made by adding fillers or solid lubricants, such as sulfurated metals, graphites, carbon fibers, carbon blacks, or PTFE to an appropriate polmeric matrix. The function of these fillers or solid lubricants is to reinforce the mechanical strength of the matrix. Although mechanical strength is increased by the addition of fillers or solid lubricants, the friction coefficient of the self-lubricating material is also increased, resulting in an increase in the wearing rate of the self-lubricating material. In view of this, self-lubricating materials containing both liquid lubricants such as greases and fillers or solid lubricants have also been developed for the manufacture of bearing members. However, friction coefficients of bearing members made from the above self-lubricating material have not been satisfactory. For example, under the following conditions: allowable highest load 200 kg/cm.sup.2, allowable highest speed 70 m/min, allowable highest PV 2000 kgf/cm.sup.2 m/min, and a temperature of -40.degree. C.-+80.degree. C., a self-lubricating bearing member, which uses polyoxymethylene as a matrix and contains more than 4 wt % of grease, has a tested friction coefficient greater than 0.05.
Most conventional matrices used for self-lubricating bearing members are prepared from the abovementioned polyoxymethylene (POM) resin, which is a kind of thermoplastic resin. Thermoset resins have not yet been used as matrices for self-lubricating bearing members. Furthermore, conventional fillers or solid lubricants, such as graphites and carbon blacks, are black in color, and the self-lubricating bearing members made from these conventional fillers are also black.